A large part of our research program is synthesis of fragments of complex polysaccharides that are part of pathogenic bacteria and study their binding with antibodies. We then identify immunodominant epitopes in said polysaccharides, chemically synthesize oligosaccharides representing these epitopes, and prepare them in form of glycosides which bear aglycons suitable for linking to proteins. After conjugation of these haptens to suitable carriers, we evaluate the neoglycoconjugates obtained as synthetic vaccines for infectious diseases caused by bacterial pathogens, using small animals as hosts. In continuation of our work on synthesis of immunogens for Vibrio cholerae O:1 antibodies, we have prepared a spacer-equipped hexasaccharide fragment of the O-PS of Vibrio cholerae O:1, serotype Ogawa and linked it chemically to CRM 9 as a carrier protein. CRM 9 is an analog of tetanus toxoid having molecular mass ~58,000 DA, as determined by MALDI-TOF mass spectrometry. The synthesis of the hexasaccharide conjugate required 32 synthetic steps. The neoglycoconjugate obtained contained, in average, four hapten residues per mol of CRM9, as shown by MALDI-TOF mass spectrometry. When neonatal mice were immunized with the hexasaccharide neoglycoconjugate, using a standard protocol, it was found immunogenic, the elicited antibodies showing specificity for the LPS of Vibrio cholerae O:1. This was in contrast to the similar neoglycoconjugate prepared from the corresponding monosaccharide hapten, which was not immunogenic in neonatal mice. This, in spite of the monosaccharide hapten showing only slightly lower binding energy and Ka than the hexasaccharide, when binding of these ligands was evaluated with monoclonal anti Vibrio cholerae O:1, serotype Ogawa antibodies. - Synthetic Carbohydrate Antigens, Antibodies, Neoglycoconjugates, Oligosaccharides, Polysaccharides, Vaccines, Vibrio cholerae, cholera,